The chat about the oil is rather by-the-way for the original poster, and the
switch closes in 3rd and 4th rather than opening in 1st and 2nd. I suppose
it could be taken to be like the old glass half full/half empty thing, but
in that case you would need to include 'reverse' with '1st-2nd',
particularly since disabling the o/d in reverse it the most important
function of the gearbox switch.
If you can make the o/d cut in and out by pulling the gear lever around a
bit while in 3rd or 4th it is almost certainly the gearbox switch. Do you
have the gear-lever mounted manual switch? If so be aware that the wiring
to these can give trouble because of the continual waggling about.
PaulH.
----- Original Message -----
From: Max Heim <mvheim@studiolimage.com>
To: MG List <mgs@autox.team.net>
Sent: Wednesday, June 21, 2000 4:40 PM
Subject: Re: Overdrive woes
> Hmmm, could it be temperature related? My understanding is you should use
> single weight motor oil in the OD transmission. I use 30wt. Or...
>
> ...possibly the 1st-2nd lockout switch is flaking. Either the switch or a
> wire connecting to it is opening temporarily, maybe related to vibration
> at that RPM. Tough to get at the switch in a '77, though...
>
> delling3 had this to say:
>
> >I have a MGB fitted with a LH type overdrive. I recently started having
a
> >problem with the overdrive "cutting out", and am looking for some help.
> >
> >Symptoms are noticable in either 3rd or 4th while in overdrive. While
> >cruising under moderate load - not accelerating hard, or lugging at low
> >R.P.M., the overdrive will begin to drop out. It is an intermittant
> >situation, the engine will load up momentarily as the overdrive drops
out,
> >then the RPMs fall again just as quickly. The symptoms occur only in
> >overdrive (the clutch isn't slipping), and seems to be possibly
influenced
> >by either R.P.M. (around 3500 R.P.M. engine speed) or temperature (more
when
> >car has been run for a while).
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